Devices for locking or otherwise engaging umbrellas to tables are known in the art. For example, U.S. Pat. No. 2,743,146 illustrates an umbrella retainer for an elongated rectangular table using the pole of the umbrella passing through the table as one leg. A sleeve slides over the pole of the umbrella underneath the table surface and is held in place on the pole by a clamp screw. The other end of the table is held up by two folding legs. And, U.S. Pat. No. 4,353,659 discloses an umbrella locking sleeve in the center of a round table. A screw presses against the post of the umbrella to lock the sleeve in position in the center hole of the table. In a related technology, U.S. Pat. No. 1,856,000 shows a holder for a tree, bush, or flag staff having a sleeve which surrounds the trunk or staff, a pin which impales the trunk or staff, and a padlock which secures the pin in place to prevent surreptitious taking of the article.
Regarding the present invention, outdoor picnic-type tables having holes in their tops to receive an umbrella have been known for years and are generally inexpensive. A typical configuration would consist of a circular dining table with a centrally installed umbrella which provides shade for diners. With the advent of interior smoking bans at business establishments, restaurants, and the like, expensive tables with center holes for use with expensive table umbrellas have evolved. A typical table can cost $1,000 and a typical umbrella can cost $500. More elaborate models are available at double these costs. Expensive metal umbrellas that look like conventional table umbrellas have also been developed.
Theft of these expensive umbrellas has become a major problem. It is toward the solution of this theft problem that the locking device of present invention is directed.